sctp: refactor sctp_outq_teardown to insure proper re-initalization

Jamie Parsons reported a problem recently, in which the re-initalization of an
association (The duplicate init case), resulted in a loss of receive window
space.  He tracked down the root cause to sctp_outq_teardown, which discarded
all the data on an outq during a re-initalization of the corresponding
association, but never reset the outq->outstanding_data field to zero.  I wrote,
and he tested this fix, which does a proper full re-initalization of the outq,
fixing this problem, and hopefully future proofing us from simmilar issues down
the road.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
Tested-by: Jamie Parsons <Jamie.Parsons@metaswitch.com>
CC: Jamie Parsons <Jamie.Parsons@metaswitch.com>
CC: Vlad Yasevich <vyasevich@gmail.com>
CC: "David S. Miller" <davem@davemloft.net>
CC: netdev@vger.kernel.org
Acked-by: Vlad Yasevich <vyasevich@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/outqueue.c

@@ -224,7 +224,7 @@ void sctp_outq_init(struct sctp_association *asoc, struct sctp_outq *q)
 
 /* Free the outqueue structure and any related pending chunks.
  */
-void sctp_outq_teardown(struct sctp_outq *q)
+static void __sctp_outq_teardown(struct sctp_outq *q)
 {
 	struct sctp_transport *transport;
 	struct list_head *lchunk, *temp;
@@ -277,8 +277,6 @@ void sctp_outq_teardown(struct sctp_outq *q)
 		sctp_chunk_free(chunk);
 	}
 
-	q->error = 0;
-
 	/* Throw away any leftover control chunks. */
 	list_for_each_entry_safe(chunk, tmp, &q->control_chunk_list, list) {
 		list_del_init(&chunk->list);
@@ -286,11 +284,17 @@ void sctp_outq_teardown(struct sctp_outq *q)
 	}
 }
 
+void sctp_outq_teardown(struct sctp_outq *q)
+{
+	__sctp_outq_teardown(q);
+	sctp_outq_init(q->asoc, q);
+}
+
 /* Free the outqueue structure and any related pending chunks.  */
 void sctp_outq_free(struct sctp_outq *q)
 {
 	/* Throw away leftover chunks. */
-	sctp_outq_teardown(q);
+	__sctp_outq_teardown(q);
 
 	/* If we were kmalloc()'d, free the memory.  */
 	if (q->malloced)